Post on 06-Jan-2018
description
How networking works
How IP resolving worksHow takeover works
How multicast really works
How IP subnetting works
Physical
Ethernet
Internet Protocol
UDP/TCP/SCTP
SIP
How networking works
Cables, fibers
MAC addresses
IP addresses
Adds ports
Application logic
Ethernet II frame Internet Protocol frame
How IP subnetting works
How IP subnetting works
Default gateway’s address & Netmask === ALWAYS EQUALS === Source IP & Netmask (otherwise, computer will report Network unreachable)
Source IP: 194.90.71.93Destination IP: 194.90.71.4Netmask: 255.255.255.0 (CIDR /24)Source IP & Netmask = 194.90.71.0Destination IP & Netmask = 194.90.71.0
Source IP & Netmask == Destination IP & Netmask -----> Send directly, without going through default gateway
Source IP: 194.90.71.93Destination IP: 199.203.72.5Netmask: 255.255.255.0 (CIDR /24)
Source IP & Netmask != Destination IP & Netmask -----> Not same subnet, send via default gateway
How IP resolving works
A user (human) sends a ‘dash’ to 194.90.71.5, which
is on the same subnet
Source endpoint broadcasts a who_has
request
Destination returns is_at reply with its MAC address
When IP address has been resolved, ICMP is
sent directly
‘arp –a’ displays current arp entries.
How takeover works
bax1 bax2
Router
ping
ping
pingpong pong
pong
active
How takeover works
ARP service_ip is_at bax1
bax1 bax2
Router
ping
ping pong
active
How takeover works
X
bax1 bax2
Router
ping pong
active
How takeover works
ARP service_ip is_at bax2
How multicast really works
How multicast really works
Bit 31
Bit 30
Bit 29
Bit 28
Bit 27
ClassLowest AddressHighest Address
0xxxxClass A0.0.0.0 127.255.255.255
10xxxClass B128.0.0.0 191.255.255.255
110xxClass C192.0.0.0 223.255.255.255
1110xMulticast224.0.0.0 239.255.255.255
11110Reserved240.0.0.0 247.255.255.255
How multicast really works
D
C
B
A
ReallyBig
Router
Server ‘A’ sends a packet to 224.1.2.3
ISP
ISP
How multicast really works
D
C
B
A
ReallyBig
Router
Router knows that this is a multicast address, and sends the packet to all of his servers, including the source.
ISP
ISP
This is the end.
I hope you liked the show.
If there are any corrections, feel free to modify and distribute under the GPL license.
Copyleft © Gil Megidish, 2005